Electron tube apparatus



Feb. 13, 1962 Filed Feb. 6, 1953 R. L. JEPSEN ETAL ELECTRON TUBEAPPARATUS FIG.2

2 Sheets-Sheet 1 INVENTORS ROBERT L.JEPSEN FREDERICK L.SAL|SBURY CURTISE. WARD RY M ATTORNEY Feb. 13, 1962 R. L. JEPSE-N ETAL ,ELECTRON TUBEAPPARATUS 2 Sheets-Sheet 2 Filed Feb. 6, 1953 FlG.3

M m u m m U MN N V AD B NESR O I .A I T ELW fl .K A LmE TR EF DT BER ORUY RFC B United States Patent Oilrice 3,021,447 Patented Feb. 13, 19623,021,447 ELECTRON TUBE APPARATUS Robert L. Jepsen, Palo Alto, FrederickL. Salisbury, Redwood City, and Curtis E. Ward, Palo Alto, @ahfi,assignors to Varian Associates, San Carlos, Calif a corporation ofCalifornia Filed Feb. 6, 1953, Ser. No. 335,438 13 Claims. (Cl.315-5.19)

This invention relates, generally, to electron tube apparatus and theinvention has reference, more particularly, to novel apparatus of thistype embodying component improvements appl'cable to velocity modulationtubes, traveling wave tubes and other tube types.

Ultra high frequency devices as of the velocity modulation type arebeing widely used as oscillators, amplifiers, modulators, etc., andheretofore have been delicate tubes assembled from a relatively largenumber of subassemblies having many small and delicate elements therein.The construction of these known devices has very often required the useof glass for the man body portion and has been such that carefulhandling and protection from even minor shock have been necessary whenusing these devices. These devices, because of their construction frommultiple subassemblies and the number of elements in each device, havebeen larger and more cumbersome than necessary for eflicient operation.Present day requirements, especially in the fields wherein the tubes aresubjected to rough usage, demand electron devices which will be bothcompact and extremely rugged While still possessing improved operatingcharacteristics over known devices.

Several difficulties encountered in discharge devices of the electronbeam type, such as, for example, klystrons and traveling wave tubes,heretofore employed arise from an interact'on between the electron beamand ions trapped along the path of the beam. These difiiculties mayinclude:

(1) Modulation of output power, frequency, and beam current at thefrequency or frequencies of continuous ion oscillation. Thesefrequencies are, typically, in the range of .l megacycle per second tomegacycles per second.

(2) Modulation of output power, frequency, and beam current at both (a)ion oscillation frequencies (in the megacycles per second range) and (b)low frequenc'es (typically in the audio frequency range). The lowfrequency fluctuations are associated with the high frequency ionoscillations.

(3) Changes in output power, frequency, and beam current as thefrequency of an applied modulating voltage is varied. These changesoccur when the modulating frequency is near one of the frequencies ofinc pient ion oscillation. The changes may be abrupt or fluctuating.

As stated above, these difiiculties arise from an interaction betweenthe electron beam and ions trapped along the path of the beam. In reflexklystrons these ions are trapped in the re-entrant tube portion betweenthe accelerator grid and the first resonator grid.

It is, therefore a principal object of this invention to provide a novelelectron tube apparatus that is both compact and extremely rugged, whileat the same time operably improved over existing electron devices ofthis type.

Another object of this invention is to provide an electron beam tubewhich is made up of a relatively few number of small subassembliessecurely and compactly assembled together to form a small and ruggedstructure, each subassembly being made up of a relatively few elements,each rugged in its own right.

Another object of this invention is to provide an electron beam tubehaving a novel structure located in the electron beam path andassociated with a portion of the tube which ordinarily traps positiveions therein, this novel structure substantially reducing the number ofions trapped therein.

A further object of this invention is to provide an electron beam tubewherein one of the walls forming the portion of the tube in the path ofthe electron beam which normally traps ions is a novel grid structurewhich permits the escape of the ions from the trap.

A further object of this invention is to provide a novel electron beamgun assembly which is structurally better than conventional gunassemblies in that it is more compact and rigid while at the same timeprovides the maximum electron emission with relatively lower heatercurrent.

Other objects and advantages will become apparent from perusal of thefollowing specification taken in connection with the accompanyingdrawings wherein one embodiment of the invention is depicted.

In the drawings,

FIG. 1 is a plan View of a reflex klystron embodying this invention,

FIG. 2 is a longitudinal sectional view of the reflex klystron shown inFIG. 1 showing a novel cathode gun assembly n plan view,

FIG. 3 is a transverse sectional view of the tube in a plane indicatedby section line 33 in FIG. 1, the arrows indicating the direction inwhich the view is taken,

FIG. 4 is a sect'on view of the novel cathode gun assembly shown in FIG.2,

FIG. 5 is a transverse sectional View of the novel electron beam gun ina plane indicated by section line 55 in FIG. 4, the arrows indicatingthe direction in which the view is taken, and

FIG. 6 is a longitudinal part sectional view of the reflex klystron in aplane indicated by section line 6-6 in FIG. 1, the arrows indicating thedirection in which the view is taken.

Referring to the drawings, the main body 1 of the reflex klystron is aunitary structure of metal such as steel comprising a block 2 having arectangular shape and having oppositely extending end port ons 3 and 4cylindrical in shape protruding from the larger sides of the block 2.The body has a multi-diarneter bore ex tending longitudinally throughthe body and axially aligned therein, the different diameter portions ofthe bore arranged in pyramided step-like relationship. Located in thewall of one other side of the block is an elongated pan-shaped recess 5having tapering side walls and a flat bottom surface in which is locatedan elon gated opening 6 or iris extending into the smaller diameterportion of the bore of the body.

1 A unitary metallic header 7 serves the triple function of providingthe mounting support for the accelerating grid 8 and the first resonatorgrid 9, providing boundary walls for the cavity resonator 10, andforming the reentrant tube 11 of this reflex klystron. This header 7 isring-shaped with a projecting annular portion 12 and a two-step axiallyaligned bore therein, this bore forming the re-entrant tube of thisklystron. Fixedly mounted as by gold brazing on one side of this header7 and axially aligned with the bore therethrough is a roundhoney-cornbed accelerating grid 8. Fixedly mounted as by gold brazing onthe opposite side of the header 7 on the projecting annular portion 12is a round honey-combed copper resonator grid 9, the longitudinalthickness of this resonator grid being of the order ,of .04" thick, orapproximately four times the thickness of the accelerating grid 8. Thismetallic header 7 and copper grids 8 and 9 form one subassembly, thissubassembly being slipped into the portion of the body 1 having the.smallheader 14 having anaxiallyaligned bore therein.

second s'ubassembly is placed within the smallest diame-g a '3estLdiameterat a point adjacent to the iris 6 and secured therein as bysilver brazing.

A second round honey-combed resonator grid 13 is mounted as by goldbrazing on a cup-shaped met ailklliic the headers, one surface of theheader 7 and the annu-. lar' portionlZ thereof, the two resonator grids9 and 13,

and one surface of the header 14.

The third or reflector "subassembly comprises a shallow cup-shapedmetal, such as nickel, reflector 15 which may.

begspotwelded toithe end flange of a conducting collar 16,, this collarin turn encompassingone end of arhollow' conducting post 17,rthepost'beingsecured as by spot-. welding within the collar 16., Thereflector mounting 'post 17 is fixedly secured and sealed withinthemounting cup-18; byva glass-to metaltype seal '19. .A wire reflectorlead or terminal 21 extends into the hollow reflector post 17,the;e'nd'of the post being cn'mp'edaround the lead,

thcgjunction being sealed and secured as by silver brazing. T

This reflector subassembly is then mounted within the re-i flectorrendofthe unitarytubebody 1,.the outer flange 22 r of ,the mounting cup 181being fixedly secured Within the largest diameterbore' of the metal body1 aslby silverbrazing. "A small hole 23in the reflector 15permitsievacuation of the space within thehollow reflector post 17during evacuation of the tube. a

a ,The fourth or cathodet subassembly is a novel cathode gun assemblywhich is extremely rugged and is more compact than heretofore existinggun assemblies.- It should be noted thatthis novel cathode gun assemblyis mounted entirely within the small metaltbody or" the tube and. thusreduces thelength of'the tube device by about one-fourth as comparedwith klystrons having the samesize body l but utilizing conventionalbeamigun assemblies which protrudefromtthe end ofrthe body 1-.

FIG. 4) having a slightly concave shape and an annular flange 47encircling the periphery thereof. This cathode button islcoated with aconventional electron emissive oxide, substance 1 and is. mounted on acathode mounting member 48 made of a strong but poor thermal conductingmaterialsuchas a metal alloy; This member has a twostephollow'cylindrical-like shape closed at one end 49. The surfacexof the closedend preferably has the same concave'curvature asthevcathode'button. Thecathode button is'niounted above this surface as by spotwel ding theinside wall of the cathodebutton flange 4710 the outer upper wall of themounting member 48. The heater wire-51 is sandwichedrinrthe narrow spacebetween the undertsurface ofv'the' cathode button 46 and the upper;surface of vthe end 49 of the mouting'member 48'. The sandwiched heater.wirer51 extends in a wavy or sinuous fashion to and-fro in this smallspace, doubling bacleon itselfjto thereby provide aniaximum length ofwire under the cathodefbutton asshown in' FIG. 5. derstood that. theheater wire couldbe wound in a flat spiralunder the cathode button or.could assume other configurations. The ends or the heater wireextenddown throughthe mounting member through two openings in the'closedtendthereofe A disk-like heat reflector 52 as of nickel is spotwelde'd orotherwise secured on theunder surface of the stepin the member 48. Thisreflector 52 also has two openings :therein to allow passage-through ofthe heaterwire 51.v This mounting-member 48 is then secured within thecylindrical focussing ring 53 as by spot- Welding theofuter surfaceofithe larger diameter. portion This cathode gun-as-- sembly comprises acathode button 46-as of nickel (see of the cylindrical mounting member48 to the inside surface of the focussing ring 53. 7 One end of theheater wire is preferably spotwelded to a nickel ribbon 54, the otherend of the nickel ribbon being similarly spotwelded to the heatreflector 52. The inner open end of the cathode assembly supporting cup55is closed with a glass-to-metal seal through which five leads extend;three of theseleads a being combination electrode terminals and mountingwires and the remaining tw'obe'ing mounting wires. The cathode gunassembly is mounted on the lattertwo mounting wires 56 and 57 and one ofthe other wires 58, which is the common terminal for th getter, cathodeand heater.

A' ribbon 59 as of nickelencircles the lower portion of the focussingring 53 m the three wires; 56,- 57 and 58 andis secured'to each -aspbyspot weldingr The getter 61 is secured at one end tothe common terminallead '58 and at the other endto the getter terminal lead 62 as byspotwelding. The fifth ,terminal lead 63 is secured as'by' spotweldingtoa ribbon 54 asof nickelwhich'in turn is spotwelded to one of the endsofithe heaterwireSI. The

the vfocussing ring and the cathodemounting member 48 whileat the sametime provides a large amount of heater wire in close associatioriwiththecathode button The cathode button is thusmore uniforrnly and moreintensely heated by the current in the heater wire,

greatly decreased lengths of the focussingvring and 'c'a'tliode mountingmembers the diameters of the'crosssece tions of the focussing ring 53and, cathode mounting mem ber 48'are greater than the length of theseelements and these elements are, thus far more ri gid than heretoforepossible. The possibility of vibration of the cathode button andheaterwire assembly is therefore greatly reduced. .The fifth or; outputwjaveguide assembly comprises a hollow rectangular metallic waveguidewindow, adapter 28. This adapter-is flanged, on oneendandhas four smallshelf-like ;indentations .29 in theside; thereof. A rectangularwindowcup -31 has a sheet'of glass 32- sealed across the openinginthe,end thereof, ,The window cup 31 is set within the open end of the windowadapter, 28 resting-on the shelfl-like indentations 29, and is sealedtherein as-by silver brazing. This window; assembly is then mounted onthe surface of -the-tube body surrounding the iris 6, the flanged'endofthewindowl adapter 28 being secured asiby'copper goldbrazingto thebody.- A rectangular sectiontof waveguide 33 made of; suitable alloysiorimetal; is secured {as by copper-gold brazing-l to a waveguide flange34,'this flange 34,prc rvidingforconnec-v tion.to ;a standard outputwaveguidecir'cuit; A pair of tube support; brackets135v .and 36t arebrazedtat one end thereof to ,the,:,fiange;34, thei -brackets extendingflush against the larger sides of the block 2 and being fastened I andis secured ,thereinasby. brazing, this tube serving as It should be unfrom the cathode button 25.

the point' of evacuation; of :thetubem After-evacuation the end of thetube iscrimped and sealed closed.

In operation of this device, a heaters-current is supplied to.theheater'wiref26:topproduce arstream 10f electrons The accelerating grid-8is at apositivepotential withiresp'ectlto the cathode'and the electronsare attracted.tosthisregionend accelerated, the electrons vreachingsa.constant'velocity in there-entrant tube '11 .formed by the header .7.The electrons pass the gap-to velocity v modulate these electrons} 1 The'ne'ga- Because of the tively charged reflector 15 repels theapproaching electrons and turns them about, the electrons then passingthrough the resonator gap between the resonator grids in bunches andgiving up high frequency energy to the field in the cavity resonator 10.The electrons thereafter are collected on the walls of the tube and thefirst resonator grid 9. The first resonator grid is made thick tothereby intercept a large number of electrons passing through on theirreturn trip from the reflector to the cathode area and thus reduce thenumber of multiple transit electrons. The high frequency power producedin the cavity resonator passes through the iris 6 into the waveguidesection and then through the glass seal to the output waveguide circuit.

In heretofore existing reflex klystrons, an ion trap is formed in there-entrant tube by the accelerating grid and the first resonator grid.The positive ions, produced, for instance, by collision of the electronsand gas molecules, are collected in the re-entrant tube and perturb theelectron beam, thus giving rise to the above noted difiiculties. A novelstructure is shown herein which greatly reduces the number of positiveions trapped within the re-entrant tube portion to thereby eliminatethese difiiculties and in addition spread the center of the beam. Thisnovel. structure comprises an accelerating grid 8 including an annularframe 41 (see FIG. 3) and a network of honey-combed vanes 42 as ofcopper supported by and extending within the frame 41. The intersticesformed by the intersecting vanes 42 of the positively chargedaccelerator grid 8 provide a relatively intense.

electric field for coacting With the beam. Located approximately in thecenter of the honey-combed vanes is an enlarged polygonal opening 43.This polygonal opening 43 in the positively charged accelerator gridpermits the positive ions in the re-entrant tube to pass therefromthrough the positive region of the accelerating grid to the negativelycharged cathode area where they are collected on the various tubeelements. Neither the size, nor the position, nor the shape of thisopening 43 in the grid is absolutely critical for any particularembodiment, the only requirement being that the opening is about in thecenter of the grid and is of the proper size and shape to preventtrapping an excessive number of positive ions in the remnant tubeportion. In the present embodiment of this invention an acceleratinggrid having an overall diameter of about .26 was employed. The insidediameter of the grid frame 41 was about .19" while there wereapproximately 190 holes in the honeycombed vanes. The larger opening inthe center of the honey-combed vanes was approximately .05". The size,shape and/ or position of the opening 43 will vary depending on eachparticular application of this invention. This special type of grid maybe utilized wherever ion traps may occur in various types of electrondischarge tubes other than this particular reflex klystron embodying theinvention as, for example, in drift spaces in multi-cavity klystrons.

Since many changes could be made in the above construction of the novelelectron tube apparatus and many apparently widely different embodimentsof this invention could be made without departing from the scopethereof, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

What is claimed is:

1. In an electron beam discharge device, a main body comprising arectangular metallic block having oppositely extending cylindrical endportions protruding from two opposite sides of the rectangular block,the body having an axially aligned bore extending through thecylindrical end portions and the rectangular block, the body having aslit-like window opening on one other side of the rectangular blockextending perpendicular to the axis of the bore, a metallic cylindricalheader having an axially aligned bore therethrough defining a re-entranttube within the header, an accelerator grid fixedly mounted on thisheader at one end of the bore and a first resonator grid fixedly mountedon this header at the opposite end of the bore, the header andassociated grids being mounted within the bore of the body adjacent thewindow opening, a second round metallic header having an axially alignedbore therethrough and a second resonator grid mounted thereon, thesecond header being mounted within the bore of the body adjacent to andon the opposite side of the window from the first header and sopositioned as to provide a predetermined spacing between the first andsecond resonator grids, whereby the bore of the body, the surfaces ofthe two headers, and the two resonator grids form a resonator cavitywithin the body having the window in the side wall thereof.

2. An electron beam discharge device including a main body comprising arectangular metallic block and oppositely extending cylindrical endportions protruding from two opposite sides of the rectangular block,the body having an axially aligned bore extending through thecylindrical end portions and the rectangular block, the body having aslit-like window opening in one side of the rectangular block extendingperpendicular to the axis of the bore, a metallic cylindrical headerhaving an axially aligned bore therethrough defining a drift spacewithin the header and an accelerator grid and a first resonator gridfixedly mounted on the header at opposite ends of the bore therethrough,the header and associated grids being mounted within the bore of thebody adjacent the window opening, a second round header having anaxially aligned bore therethrough and a second resonator grid mountedthereon over this bore, the second header being mounted within the borein the block of the body on the opposite side of the window from thefirst header with the second resonator grid closely adjacent the firstresonator grid, a reflector assembly comprising a reflector mounted on amounting post, the mounting post being fixedly mounted within the borein the outer end of one of the cylindrical end portions of the body withthe reflector extending into the bore of the body and closely spacedfrom the second resonator grid, a cathode gun assembly mounted withinthe bore of the body at the outer end of the other cylindrical endportion with the cathode gun extending inwardly into the bore of thebody and closely spaced from the accelerator grid, and

an output Waveguide section mounted at one of its ends on the blockportion of the body and encircling the iris window, the other end of thewaveguide being closed by a glass-to-metal seal.

3. A cathode gun assembly comprising a cylindrical focussing ring, anelectron emissive cathode and a heater wire mounted within the focussingring, a cylindrical cathode assembly supporting member having open endsand a glassto-metal seal across one of the open ends in the member, aplurality of mounting wires extending out from the supporting member andimbedded in the glassto-metal seal, the wires engaging the outer surfaceof the focussing ring at spaced points around the ring, and a metallicribbon encircling the focussing ring and the mounting leads and securelyaflixed thereto to thereby rigidly hold the focussing ring, cathode andheater wire in fixed position with respect to the supporting member.

4. A cathode gun assembly comprising an electron emissive concavedisk-shaped cathode button having a flange around the peripheral edgethereof, a cylindrical cathode mounting member having a closed end witha concave surface, the cathode button being mounted over and spaced fromthe closed end of the mounting member with its flange engaging the outersurface of the cylindrioal mounting member and being aflixed thereto, aheater wire positioned between the cathode button and the closed end ofthe mounting member and arranged to occupy the major portion of thespace therebetween, the ends of the heater wire extending throughopenings in the closed end of the mounting member, and acylindricalcfocussing ring, the cathode mounting; memb eribt:

ing fixedlyrse'cured the focussing ring with its outer surfaceengagingthe inner surface ofthe ring, the cathode button extendingwithin the lfocussi'ng ring.

SI'In anelectron beaml discharge device havingmeans for'producing a'beamof electrons, rahollow enclosure positioned in the'path of thebeamzhaving open ends through which the beam enters and leaves thehollow enclosure a first grid closing one end of'said enclosureyand asecond grid mountedover theother-open end of the enclosure, saidsecond'grid' having aplurality of inter-= for producing a beam ofelectrons, are-entrant tube in the path of the'electron beam comprisingside walls and a pair of grids mounted on each'end ofthe r e-entranttube'transverse to' the path ofthe beam, on'e of said grids being. ahoney-combed accelerator grid adjacent the cathode region ofthe device,said accelerator grid having a plurality of: intersecting vanes thereindefining. small interstices there-i between providing a relativelyintense electric" field in use forcoactingwith the beam and havinganenlarged opening approximately in the center ofthe' grid vane'networkgreatly larger than -any of the other'interstices throughwhich'ionstrapped in the re-entrant tube can be drained intothe' cathoderegion; 1 a I a, {-7-5Ai1 electrondischarge device comprisinga mainbody,

havingfan --axially' aligned-bore! extending therethrough and having-aslit-like window opening'inthe side thereof extending perpendicular tothe axis of the bore, an an nular rnetallic headerlincluding -a hollowcylindrical reentrant 'tube portion, the bore of said re-entranttubebeing axially aligned-in the bore-of the main body, an accelerator gridmounted over one end of the re-entrant tube bore'and a first resonatorgrid mounted over the other end of the re entrant tube bore, the headerand reentrant tube portions and the associated grids beingmountedw-ithin the bore'of the body adjacent thewindow opening," asecond metallic header having an axially aligned bore thereth'rough anda second resonator grid mounted overthe-bore thereof, the second headerbeing mounted 'within-thebore of 'the body adjacent to thewindow on theopp'osite' side from the first header and so positioned as to provide apredetermined spacingbetween the first'a'nd'second resonator" gridswhereby the bore oi the:bodyf-thesurfaces of the two headersiandihe tworesonator grids forming a resonatorcavity-within the body having the'w-indow in thesidewallxthereof. 7 -8. An electron beam discharge deviceincluding a body "having an axially aligned bor'e'f extending}thei'ethroughith'e bodyhavingaslit-like window opening in the sideextending perpendicular to the was of the bore,

.an annular metallic header'includinga hollowcyli'nd'rical re entranttube} portion, the bore of said re-entrant tube being axially aligned"in thebore of' the main body; an

accelerator gr id mounted over'one' endof there-entrant tubeb'or'eand'afirst resonator grid mounted'over "the one ter end-0f=the;bodyWfihlhifl'fifiQCtQK x end ng-int he here etthebodyand clqse r pa erolmit s e ond resona o ig c hode :gun assembly.,ng ume s the bo e-Letthe b dy: t: h t e 0u en w t the cathodegun extending-inwardly into thebore of;the-body closely spaced from the accel eratoriglid and a waveenergy-p eable; m erial c ve ins: he I -Wi I A r flex l y tronincludingsoathodeadapted o pro: d ce abe m of. e ectrons; at rel-entrant; tu efmmb r, c vity, r n tor, a r flector elec o t ndem. c elerator gridcoveringt-he open endof'iho re-entrant tube member near the cathoderegion,t.-the grid being a honeycombed accelerator gridrihaving a pl iaiW i intersecting grid vanes thereindefining small intersticestherebetween and having an enlarged-openingapproximatelyin the center ofthe ,grid vane 'network'largerthanthe :other interstices through whichions in 5 the re-entrant tube 1 member may be drained into thecathoderegion. 1 a 1 I 1 T 10. A refiexk-lystron comprising cathodemeansadapted, to producea beam-of electrons directed along a path in theklystron a .r'efl'ectorelectrode; positionedinthe path adapted to repelthe electrons, a'hollow member forming a re -entrant tubepositionedinathe beam path between thecathod'e means and thereflector, acavity resonator member; positioned intheibeam path between thereentrant tube member. and the reflector including aresona-torgridmounted on the ;rleflector.end.iof the hollow re-entrant tube 'memberanda honeycombed accelerator gridmounted on the cathode end of -the hollowre-entrant tube member having 'a plurality of intersecting vanes thereindefining small interstices therebetween and having an enlarged openingapproxhnately in the center oi the grid vanenetwork' through'whichxionsthat may normally be trapped between the gaccelerator grid and. theresonator grid in there-entrant tube f'member maybe drained to thecathode region. 7. j 1 3 V 11. An electron be 'Vdischarge'deviceincludingta main bodyvcompzising a-metallic-blockhaving oppositelyextending'cylindrical end portions sedan axially aligned bore aextending through the cylindrical end portions and the block a metalliccylindrical header mounted in the device having an ardally alignedbore'there'through defining a re-entrant ;tube:within the header; :anaccelerator grid fixedly mounted'on-thisheader atone end of the bore anda first-aresonator-g'rid; fixedly mounted on this header at the.oppositea'end of the boreg'said accelerator grid being ahoneycombedgrid having a'plurality of intersectinggrid vanes therein defining smallinterstices therebetween and having. an enlarged opening approximatelyin the center of th'e grid vane network larger than the otherinterstices through which' ions in the 're-entrant tube 'member may bedrained-into the cathode-region, and a cathode gun assembly mounted inone cylindrical'end portion adjacent said accelerator gridicbmprising acylindrical focusing rlngyan electron emissive cathode-and a heater wiremounted within the focusing ring, a cylindrical= cathode assembly"supporting member: having open'iends and an insulator seal across' one"of 'theopenends in the member, a-plurality of mountingwires extending'ouffrbm'the supporting member and'irnbedded'in the'insulator seal,- thewires engagi'ng' theo'uter surface of the focusing ring atspaced'pointsaround the ring, and a'metallic ribbon en circling thefoeusin'g ring anddhemounting leads and securely afiixed thereto tothereby rigidly hold the focusing ring, cathode'and heaterwireinfixed-position with respea't' m nwmngmmsee f 12. electron' discharge 'fdevice jcomprising' a main body 7 having an axially i'aligne'd boreextending therethfroughgian annularlmetallicfhe'ader including a hollonc lindricalre-entranttube a v ionrnountedin body,

theborefo f tubeibeihg axially aligned in t ar f he main body, .a a q sat r e d i wi e e r n nd f h Rea ent-t bs Dema d a-fi s Yew tor and munt d q erithe a; and, it h fl w sa r hf tube bore, and a cathodestructure mounted in the bore of the body adjacent said accelerator gridcomprising a cylindrical focusing ring, an electron emissive cathode anda heater wire mounted within the focusing ring, a cylindrical cathodeassembly supporting member having open ends and an insulator vacuum sealacross one of the open ends in the member, a plurality of mounting wiresextending out from the supporting member and imbedded in the vacuumseal, the wires engaging the outer surface of the focusing ring atspaced points around the ring, and a metallic ribbon encircling thefocusing ring and the mounting leads and securely afl'ixed thereto tothereby rigidly hold the focusing ring, cathode and heater wire in fixedposition with respect to the supporting member.

13. An electron beam discharge device comprising a cathode gun assemblyfor producing a beam of electrons including a cylindrical focusing ring,an electron emissive cathode and a heater wire mounted within thefocusing ring, a cylindrical cathode assembly supporting member havingopen ends and an insulator vacuum seal across one of the open ends inthe member, a plurality of mounting wires extending out from thesupporting member and imbedded in the vacuum seal, the wires engagingthe outer surface of the focusing ring at spaced points around the ring,and a metallic ribbon encircling the focusing ring and the mountingleads and securely aflixed thereto to thereby rigidly hold the focusingring, cathode and heater wire in fixed position with respect to thesupporting membar, a hollow enclosure positioned in the path of the beamhaving open ends through which the beam enters and leaves the hollowenclosure, 2. first grid closing one end of said enclosure and a secondgrid mounted over the other open end of the enclosure adjacent thecathode gun assembly, said second grid having a plurality ofintersecting grid vanes therein forming a honeycomb configurationdefining small interstices between the vanes and having an openingapproximately in the center of the grid vane network having a diametergreater than three times that of the other interstices through whichions trapped in the hollow enclosure are drained into the cathoderegion.

References Cited in the file of this patent UNITED STATES PATENTS

